Electrical properties of hornet silk: temperature dependence.

Hornet silk is a polymer of amino acids. One of the known properties of polymers is their electrical activity. The present study describes the results of electrical measurements carried out vertically on the silk cap of pupae of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). The measurements undertaken were the temperature-dependent electric current, voltage and resistance, all measured within the range of biological temperatures, as well as the capacitance. The temperature-dependent spontaneous current attained values up to 327 nano Amperes (nA) while the maximal voltage reached 347 millivolt (mV). The electrical resistance was low and steady (1-20 mu omega) at temperatures ranging between 19-32 degrees C, but at lower or higher temperature it increased fairly sharply by about three orders of magnitude. The electrical capacitance, computed according to the discharge curve (decay curve) amounted to 0.4 microFarad (microF). The paper also discusses the role of the pupal silk as producer of a 'clean room' while the cuticle is being laid down by the pupae after undergoing metamorphosis, as well as the significance of the measured electrical parameters vis-à-vis the developing pupae.